Colored photographic image and method of producing same



Aug. 7', 1934.

H. D. MURRAY El AL 1,968,956 COLORED PHOTOGRAPHIC IMAGE AND METHOD OFPRODUCING SAME Filed May 9 1931 Patented Aug. 7, 1934 up COLOREDPHOTOGRAPHIC macs ABID METHOD OF PRODUCING SAIHE Humphrey Desmond Murrayand Douglas Arthur Spencer, South' Kensington, London, England,assignors of one-third to Colour Photographs (British and Foreign)Limited, London, England, a company ofEngland 1 Application May 9, 1931,Serial No. 536,306

In Great Britain June 20, 1930 16 Claims. (01. 95-88) The presentinvention is for improvements in colored photographic images and themanufacture of same and concerns the manufacture of colored images inazo-dyestufis. The invention is adaptable to the twoor three-colorprocess of color-photograph production, and is particularly applicableto the manufacture of colored films utilizable for cinematographicpurposes.

The process of the invention consists essentially in this, that adiazo-compound is combined or mordanted with a metal salt image, forexample, a silver-salt image, which may be produced according to theknown methods of the photographic art, and the diazo-complex is thencoupled with an azo-dyestufi coupling-component of the type requisite togive the color desired. By repeating the process with anotherimage-support, for example, a film, or upon the other side of the samesupport, with appropriate variation in the .dyestufl components, twosuperimposable, or two superimposed, colored images may be obtained; andby similarly treating a third support, three differently coloredsuperimposable images may be produced.

The invention will hereinafter be described in its application to theconversion of silver-salt images, which may be obtained by any of theknown processes of photography, into azo-dyes. It is to be understood,however, that the invention is not limited to treatment of an imagecomposed of a salt of silver but is broadly applicable in this respectto the treatment of an image composed of a salt of any equivalent metalto silver, that is to say a metal which is capable of being convertedinto a water insoluble salt by bleaching when coated in a gelatine orother colloid layer.

We have found in our researches that when anoriginal silverimageisconverted by any of the processes of photography known as bleachinginto an insoluble silver salt or an insoluble complex-possibly a doublesalt-of silver and another metal, such insoluble silver derivative maybe caused to combine with a diazo-compound, and the diazo-group in theresulting product can, in its turn, be coupled with an azo-dyestuif.coupling-component to yield a dye.

The invention, therefore, comprises as a new article of manufacture asupport, for example, a

mm, carrying upon one or both .of the surfaces a photographicallyproduced metal salt image in union with a diam-complex in a, conditionto couple with an azo-dye coupling-component to give an azo-dye.

Advantageously, the coupling-bath for production of the azo-dy'ecomprises a substance capable of rendering thesilver salt present in thesilverdiazo-complex soluble in water. Such substances are known inphotography as fixing agents. We

have found as a general rule that, in the absence of these fixingagents, an image constituted. by a silver-salt-diazo-complex tends to beonly partially converted into an azo-dye when treated in thecoupling-bath, even when the latter is brought to the correct degree ofalkalinity for rapid coupling. This phenomenon calls for more particularregard, when depth of color, especially by transmitted light, in a givenimage or number of images, is a desideratum. The amount of azodyeproduced varied according to the nature of the coupling-component. Thus,some of the amino-naphthol-sulphonic acids in the absence of silver-saltsolvents are capable of producing an image which is superficiallycolored when viewed by reflected light, but displays little depth ofcolor when viewed by transmitted light after removal of the residualsilver-salt in the image. On the other hand, coupling-components such asthe naphthol-carboxy-acid-anilides appear to be incapable of couplingwith these silver-salt-diazocomplexes in the absence of a solvent forthe silver-salt constituent of the complex. A possible explanation isthat the former classof coupling components, being themselves capable ofcombining with the said silver-salt constituent,

dissolve the superficial layers of the image and liberate suflicientdiazo-compound to couple with the excess of azo-coupling component inthe coupling solution. In any event, a simple preliminary experimentsuffices to determine the behaviour of a given coupling-component, butour experience goes to show that, where depth of color is sought, theinclusion of a fixing agent in the coupling-bath is to be generallyrecommended. Soluble thiosulphates, cyanides and sulphocyanides aresuitable fixing agents, but the 7 metal or equivalent radical of thesalt should not be one capable of forming an insoluble derivative withthe diazo-compound, thus interfering with the normal course of thecoupling-reaction. A1- kali salts, such as those of sodium andpotassium, are convenient and utilizable, but the ammonium salts are notto be recommended as they'tend to decompose in the alkaline couplingsolution with loss of ammonia. Thiosulphates are preferable tosulphocyanides as the latter display a tendency to soften the gelatineof the emulsion.

The bleaching of the original silver image ma may be employed. Thebleaching agents may be any of those known in the photographic art, withthe proviso that, when a composite bath is used, the agent'employed mustneither decompose nor precipitate the diazo-compound. Examples ofsuitable composite baths are given hereafter. We have found it to begenerally more convenient to employ a separate bleaching bath, and thatpreferred is a 5 per cent. aqueous solution of cupric oride, which actsquickly, is stable, and is fi dily washed out from gelatine emulsions.

After bleaching, the image should be washed in distilled water or inwater very slightly acidified with acetic acid. This precaution need notbe taken when the washing water is free from salts, such as dissolvedcarbonates, liable to cause precipitation of insoluble compounds of thecopper or other metal in-the bleaching agent within the emulsion of thesilver print. Such insoluble metallic salts are capable of mordantingdiazonium compounds, and produce fog" in the finished picture.

For practical reasons, it is advisable to work with thosediazo-compounds which are reasonably stable in aqueous solutions atnormal temperature. Diazonium salts prepared from the following aminesfulfil this requirement as well as providing for a wide range ofcolors:-

p-amino-dimethyl-p-phenylenediamine. p-amino-diphenylamine.pp-diamino-diphenylamine. p-amino-triphenylamine. p-amino-diphenylurea.

To increase the stability of the solution of the diazo-compound for thetreatment of the silversalt image, said solution may comprise an acidsubstance, for example, an organic acid such as citric acid.

In our experience, it is very advantageous also to include in thesolution of the diazo-compound an agent to depress the hydrogen-ionconcentra- I tion of the solution. Such an agent is provided by theneutral alkali salts of weak acids, for example, organic acids such ascitric acid.

The azo-dyestuff coupling-component may be an amine or a phenol, aphenol-sulphonic acid, or an amino-phenol-sulphonic acid.

When coupling is effected in an alkaline solution containing anon-volatile alkali, such alkali may be provided by an alkali hydroxideor by a salt, such as sodium borate, which becomes alkaline byhydrolysis.

The coupling reaction is improvedin general, accelerated-by the presencein the coupling-solution of sodium or potassium citrate in adequatequantity. which we have found is generally above 10 per cent. Such useof a citrate is usually desirable but is not essential.

The coupling (developing) solution may advantageously also comprise anagent to increase the insolubility of the synthesized dyestuif. Suchagent may be one of those commonly used in the dyestuif-industry forsalting-out dyestuifs from solutions, for example, sodium chloride,sodium sulphate and sodium phosphate. 7

The following are examples of ways in which the invention may be carriedinto efiect, and it will be appreciated that these examples are given byway of illustration of the invention and not in limitation thereof.

Example I An untoned silver print, on glass, paper, celluloid or othersupport, is soaked in water and immersed in the following composite bathuntil the image has been converted from black to an orange color:--

A. Cuprie sulphate 30.0 gms.

Potassium citrate 200.0 gms. Potassium ferricyanide 20.0 gms. Water1000.0 0. c.

B. p-diazo-diphenylamin sulphate 3.5. gms. Water 1000.0 0. 0.

Solutions A and B are mixed just before use. The treated print iswashed, and the dye-image In place of the copper sulphate in thebleaching bath of Example I, 20.0 gms. of chromium sulphate may besubstituted; or the following bath may be substituted for the componentbaths A and B:,-- 2" Potassium ferricyanide 13.0 gms. .Lead nitrate 7.0gms. 10 per cent. acetic acid 100.0 0. c. p-diazo-diphenylaminesulphate---" 3.0 gms. Water 900.0 0. c.

An untoned silver print is bleached in a solution of copper chloride orin a solution of potassium bichromate acidified with hydrochloric acid.

After washing, the bleached print is immersed in the following.solution:-

The print is rinsed, washed in a solution of 2 per cent. potassiumiodide until the background is clear, and development then effected bytreatment with the following solution:--

Phloroglucinol 5.0 gms. Sodium biborate 50.0 gms. Sodium thiosulphate250.0 gms. Sodium sulphate 200.0 gms.

Water; 1000.0 0. c. The developed print is thoroughly washed and thendried.

The following is an example of one way of producing a picture in threecolors according to the invention:--

Example IV is to say, a developer which doesfr'not harden or color thegelatine so as to interfere with full development of the color of theazo-dye within the emulsion. The developed prints are bleached in a bathof 5 per cent. cupric chloride solution omitted 11 the sodium salt ofthe "H-acid" be used.

(3) For the yellow printing image:- water 150 c. c. Potassium hydroxide3.25 gms. Sodium thiosulphate 60.0 gins. Potassium citrate 30.0 gins.

thiosulphatein the above until no further change is observed. This takesabout 1-2 minutes. The bleached prints are washed for 10 minutes indistilled water, and then immersed in a bath made'up as follows:-

A. Water 100 c. 0.

Potassium citrate 20- gms. Citric acid 5 gms.

Potassium iodide 2 gms.

B. p-diazo-diprenyl'amine sulphate 1.0 gm.

Water 100.0 0. c.

25 c. c. of Solution 13 aremixed with 100 c. c. of Solution A and theprint treated with the mixture.

The purpose of the presence of the citric acid is, as already stated, tostabilize the diazonium salt. The mixed solution keeps two or threedays. but in the absence of the acid begins to decompose within about anhour of mixing the two solutions. 1

The prints are kept in the above sensitizing bath for -10 minutes. Alonger immersion has no appreciable effect. They are thenwashed inrunning water for 1 minute and subsequently in a 2 per cent. solution ofpotassium iodide until the background is perfectly clear. This prevents.decomposition of the silver-diazo-complex and loss of the diam-compoundfrom the image, but does not aifect the rate of washing out from thebackground. This washing takes 5-10 minutes, and may be continued up tominutes without visibly 'a'ifecting' he color of the final image in anyway. Several hours washing appreciably reduces the final color only inthe high lights. The washed prints are respectively developed in thefollowing baths:-

(1) For the red printing image:- Water 100 c. c. Borax 5 gms. Sodiumthiosulphate- 40 gms. Potassium hydroxide 0.5 gm.

Potassium citrate 20gms.

lene-3-sulpho-acid) 1.0 gm.

If the sodium salt of the "J-aci "be used, the potassium hydroxide maybe omitted. (2) For the-blue printing image:

As "before, the potassium hydroxide may be h The solution'is saturatedwith m-cresol, filtered and then diluted by addition of c. c. of waterto the filtrate.

Coupling in each of these baths is complete in about three minutes.Further immersion-has no effect upon the images. 2 guns. of potassiumcyanide or 5 gins. of potassium sulphocyanide may be substituted forevery 30 guns. of the sodium formula. In the case of cyanide thecoupling baths act rather more 'tration of sulphate ions,

phate weakly acidified quickly, but the colors produced appear to be.slightlyless transparent than those obtained when thiosulphate is used.

The prints after coupling are washed in a solution of 5 per cent.potassium alum until free from thiosulphate. This takes aboutl0'minutes. If

the prints be not washed, sodium thiosulphate tends to crystallize outon the surface on drying; and if they are washed in plain water the dyesproduced from the J-acid" and H-acid may run to some degree. By washingin 5 per cent. potassium alum, the sodium thiosulphate is displaced andthe alum drying.

The prints are finally dried,'and are then ready for superimposition fora The potassium alum prevents running in all images formed fromsulphonic acid couplingcomponents. The dissociation, and hence thesolubility, of these sulphonic acid dyestuffs can also be reduced byusing acid wash-water and having present an excess of a stronglydissociated ion such as the chloride, ion. Potamium alum is both acid(by hydrolysis) and ionizes strongly. To produce a large concenpotassiumalum may be solutionof sodium sulwith sulphuric acid, for example,one-half per cent. A strong acid solu-.

three-color effect.

replaced by an aqueous tion will soften the gelatine of the emulsion.

Sodium sulphate acidified with potassium metabi'sulphite 'may also beused as an insolubilim'ng agent. Potassium alum presents the specialrecommendations of being easily available and combining in one substancethe two insolubilizing factors.

The invention permits of the production of two separate and distinctimages toned in different colors in the same emulsion layer, one imagedisposed beneath the emulsion and the other upon the surface thereof,the following being, with reference to the accompanying drawing, anexample of this application of the invention:

Example V A supporting base 1 thickly coated with an emulsion 2 of softcharacter is stained with a dye which can be removed completely from theemulsion by washing. The dye used is one which absorbs the major portionof the light of that wave length to which the emulsion is sensitive, andthus hinders the penetration of light through the emulsion. An exampleof a dye for use with bluesensitive emulsions is quinoline yellow (B. D.(3. color index No. 801). The .base is soaked for six minutes in a 2percent. solution of the dye, rinsed very rapidly in distilled water,blotted with clean blottin -paper and rapidly dried, all theseoperations being carried out in the dark or by the light of anappropriately screened illuminant. base 1 is then clipped between twonegatives 3, 4 in register of the same object exposed behind the twofilters commonly used for two-color photography. The base is thenexposed tov a light of suitable intensity, first on the face and thenthrough the back. After development, fixing and washing, one image willbe observed to lie on the does not crystallize out on,

sulphate or phosphate surface of the emulsion 2 and the other image atthe back. Theseimages 5, 6 (see Figure 2) are now bleached in the mannerdescribed in Example IV above. They are washed in a 2 per cent.solusince the solutions penetrate thewet gelatine more quickly than whenthe latter is dry.

The dried print is placed in either the red or the blue toning bath ofExample IV, according to whether the red-printing image or theblueprinting image is on the surface of the emulsion. The length of timeof immersion is influenced by the nature of the emulsion, but for anyparticular emulsion may be determined by a simpletrialand-errorexperiment on the correct balance of color in the finishedproduct. The print is then immersed for three minutes in a bath of thefollowing composition:-

Water 100 c. 0. Potassium iodide 2 gms. Potassium alum Bgms.

and is then placed in the alternative toning bath until the coupling iscomplete; The print is then washed and dried as before. a

If the print be too short a time in the first coupling bath, that imagewhich lies at the surface of the emulsion will be toned an impure color;and if the print be kept too long in the said first bath, the imagewhich lies at the base of the emulsion will be of an impure color.

The object of the bath intermediate between the two coupling baths is,firstly, to stop by the acid-reaction of the bath, theaction of thefirst coupling-agent, secondly, to wash out the coupling-agent; and,thirdly, to prevent the diazocompound from being washed out at the sametime, this end being obtained by the presence of potassium iodide in thebath. If cyanide or sulphocyanide be substituted for the thiosulphate inthe coupling baths, the potassium alum may be replaced by a weak acid,for example, acetic acid, of a concentration such that the bathcontains1 per cent. of the acid, expressed as glacial acetic acid.

Summed up, therefore, the invention comprises the conversion of positiveimages of silver into corresponding images of transparent,water-insoluble colors substantially free from silver. A wide range ofcolors is obtainable, inter alia those suitable for twoand three-colorprojection, and many of the available colors are spectrographicallypure. The process of conversion is a chemical one capable of beingcarried to completion and the conversion of the original metallic imageinto the corresponding coloring matter may be in constantproportionality. Thus, if a number of silver positives of equal densityare treated according to the invention the resulting prints may beobtained of equal intensity of color, The process may be operatedcontinuously and rapidly; and, by appropriately adjusting the time ofthe-passage through the different baths according to their constitutionand the purpose in view, may be rendered practically automatic, thefinal effect obtained being; ceteris paribus, dependent upon the degreeof definition ofthe original metallic image. This is of greatimportance; in any method of three-color printing. The three metallicimages are balanced in printing and developing by well-known methods ofdensity control, and are then converted, practically automatically, intocolor prints in which the color balance is correct. There is here adistinct contrast with existing methods of cinematographic colorprinting in which the lack of color balance and adequate colorcontrolare frequently very apparent.

By the use of opposed rollers or like-acting relatively disposedspreading devices, both sides the surface thereof.

of the image support may be simultaneously or successively treated withthe same or a different solution. As already stated, two separate anddistinct images toned in diiferent colors may be Produced in the sameemulsion layer, one disposed beneath the emulsion and the other uponOwing to the water-insoluble nature of the colors obtainable, two ormore images may be applied to one side of the support either byrecoating or by transfer. As the process permits of the toning of twoseparate and distinct images in the same emulsion layer, a three-colorrecord on one support may be pro- I duced, with only one wetting of thesupport, by employing stock coated on both sides with 90 emulsion. Theinvention further provides for the ready realization of a wide range ofcolors, and the production at will of colors in insoluble azo-dves byreason of the formation of the latter in situ from soluble components.

The following articles may be produced by the invention:-

l. A base, for example, a film, having upon one or both of the surfacesthe combination of a metal salt image and a diazo-compound capable ofcoupling with an azo-dyestuff coupling component to give a dye.

2. A diazo complex of a. bleached metallic image capable of couplingwith an azo-dyestuff coupling component to give a dye, on a transparentwater-insoluble base toned in color.

3. An azo-dye image on a transparent waterinsoluble base, the imagehaving been produced by coupling a diazo-complex of a. bleached metallicimage with an azo-dyestuif coupling component.

4. A similar image to 3 transferred by any of the known means from awater-insoluble base to paper.

5. Two or more images according to 3 in two 115 or more colorssuperimposed to give a transparency in natural colors.

6. Two or more images according to 4 in two or more colors superimposedto give a picture in natural colors.

7. Two images according to 3 on either side of the same transparentwater-insoluble base toned in different colors to give a transparency innatural colors.

8. Two images according to 3 lying at different levels of an emulsion ona water-insoluble base and toned in difierent colors to give atransparency in natural colors.

9. Three images according to 3, two lying at different levels of theemulsion on one side (i a water-insoluble base, the third lying in theemulsion on the opposite side of the base, all three images being tonedin different colors to give a color transparency in natural colors.

Although the result of treating the metal-salt image with the solutionof the diazo-compound is referred to herein as a combination, this modeof reference is not to be taken necessarily to mean that there is acombination in the strict chemical sense. The nature of the union and01' the product is not yet known. The fact stands, however, that when ametal-salt image is treated with a diazo-compound according to thisinvention, a union of some kind takes place between the two, and theresulting complex may be caused 145 to react with an azo-dye couplingcomponent toyield a dye reproducing the original metallic image.

We claim: 4

1. The manufacture of colored images which 150 comprises bleaching asilver image, combining the bleached image with a diazo-compound, andcoupling the diazo-complex with an azo-dyestuff coupling-component.

2. The manufacture of colored images which comprises combining adiazo-compound with a silver salt image and coupling the diazo-complexwith an azo-dyestuff coupling-component.

3. The manufacture of colored images which comprises combining adiazo-compound with a bleached silver image and couplingthe-diazocomplex with an azo-dyestuff coupling-com- 4. The manufactureof colored images whch comprises simultaneously treating a silver imagewith a bleaching agent and the solution of a diazo-compound, andthereafter coupling the silver-diazo-complex with an azo-dyestuficoupling-component.

5. The manufacture of colored images which comprises bleaching a silverimage with a solution of cupric chloride, treating the rec-bleachedimage with the solution of a (Haze-compound, and coupling thesilveradiazo-complex with an az0- dyestuff coupling-component.

6. The manufacture of colored-images which comprises treating a silverimage with a solution comprising cupric chloride and a diazonium salt,and coupling the silver-diazo-complex with an azo-dyestuifcoupling-component.

'7. The manufacture of colored images which comprises combining adiazo-compound witha bleached silver image and coupling the diazocomplexwith an azo-dyestuflf' coupling-component in presence of a fixing agent,

8. The manufacture of colored images which comprises combining ableached silver image with a diazo-compound, washing the so-combinedimage with a solution of a soluble iodide, and thereafter combining thediazo-complex with an azodyestufi coupling-component.

9. The manufacture of colored images which comprises treating a bleachedsilver image with the solution of a diazo-compound stabilized by thepresence therein of an acid.

10. The manufacture of colored images which comprises treating ableached silver image with the solution of a diazo-compound stabilizedby the presence therein of an aliphatic polybasic acid.

11. The manufacture of colored images which comprises treating ableached silver image withthe solution of a diazo-compound comprising anagent to depress the hydrogen ion concentration of the diazo-compo'undsolution.

12. The manufacture of colored images which comprises treating ableached silver image with the solution of a diazo-compound stabilizedby the presence therein of an acid and comprising an agent to depressthe hydrogen ion concentration of the diazo-solution.

13. The manufacture of colored images which comprises combining ableached silver image with a diazo-compound and converting thediazocomplex into an azo-dye by treatment with a-coupling solutioncomprising an alkali citrate in concentration sufficient to acceleratethe combination of the azo-dye coupling-component with thediazo-complexof-the image.

14. As a new article of manufacture, an image support carrying on atleast one surface a bleached silver salt image in combination with anuncoupled diazo compound.

15. The manufacture of colored images which comprises bleaching aphotographically produced image composed of a metal convertible into awater insoluble salt by bleaching, combining the bleached imagewith adiazo-oompound, and coupling the diazo complex with an azo-dyestuficoupling-component. a

16. The manufacture ofcolored images which comprises simultaneouslytreating a photographically produced image composed of a metalconvertible into a water insoluble salt by bleaching, with a bleachingagent therefor and the solution of a diaz'o-compound, and then couplingthe diazo-complex with an azo-dyestuff couplingcomponent. a

f HUMPHREY DESMOND MURRAY.

DOUGLAS ARTHUR SPENCER.

